It was with understandable trepidation that the BBC's head of fiction, Jane Tranter, introduced Thursday night's premiere of The Passion, an ambitious drama about the final days of Jesus Christ, which was to be screened before the watershed on BBC1 this Easter.

In an auditorium of London's Apollo West End cinema was an ecumenical assortment of clergy, including the Anglican Bishop of London, the Right Rev Richard Chartres; the Anglican Archbishop of Wales, Dr Barry Morgan; and Father Deacon Stavros Solomou, representing Archbishop Gregorios of the Greek Orthodox archdiocese of Thyateira and Great Britain. Solomou's late arrival meant he had to sit up in the gods.

Tranter used humour to break the ice. "I normally give a potted history, but I'm not doing that tonight because most of you know the bones of this," she said. "The BBC likes a challenge and God knows it loves period drama."

She added: "Not only did we have the gospel, we had a huge amount of resource material."

It became apparent though, from the discussions following the hour-long screening, that some felt the BBC had not done enough homework. Dr Tina Beattie, a senior fellow at Roehampton University, was one of several to criticise a line delivered by Mary, played by Penelope Wilton.

In the scene she confronts Jesus, played by Joseph Mawle, and tells him: "You were in my belly before I...#8239;knew it." It was, said Beattie, "theologically wrong" to suggest Mary woke up pregnant and was unaware of what was happening to her. "The whole Christian religion hinges on freedom and Mary had the right to choose. I regret that one line."

"That's one of the interesting things about art," said Mark Goodacre, historical consultant for The Passion and an associate professor in the department of religion at Duke University, North Carolina. "A line is capable of that reading."

One of the guests remarked how the BBC's response to accusations of theological inconsistency resembled a three-line whip. "Every time someone raised a concern, there were others who started clapping and saying how wonderful the production was."

The audience then turned its attention from Mary to her son, Jesus. Mawle, the 33-year-old actor who plays him, confessed to the Guardian last night that he was a humanist. But his portrayal was so compelling he had to remind people his name was Joseph, not Jesus.

As the audience filtered out, the clergy looked bemused by the whirl of air kissing and glamour. "We only go to meetings," said Solomou as he surveyed the room. "We don't do anything like this."

Standing outside the cinema, smoking a cigarette, Mawle seemed pleased with the reception: "There were some difficult questions, but they didn't throw me to the lions, did they?"

· This article was amended on Tuesday March 4 2008. The Most Rev Barry Morgan is the Anglican, rather than Roman Catholic, Archbishop of Wales as we said in the article above. Mark Goodacre is no longer a senior lecturer in the New Testament at Birmingham University. He left that post in 2005 and is now an associate professor in the department of religion at Duke University, North Carolina. These errors have been corrected.